1. Field of the Invention
The present invention relates to a high voltage detecting circuit, in particular, to a high voltage detecting circuit included in a semiconductor device having terminals, for generating a control signal in order to start a specific mode of the semiconductor device, when a potential of a specific mode signal higher by a predetermined value then a normal input voltage having a predetermined range, is applied to at least one of the terminals of the semiconductor device.
2. Description of the Related Art
In general, a high voltage detecting circuit is included in a semiconductor device for detecting a potential of a terminal of the semiconductor device. When the potential of the terminal of the device is higher by a predetermined value than a normal input voltage having a predetermined range, the high voltage detecting circuit generates a control signal for starting a specific mode of the semiconductor device. Upon receiving the control signal, the semiconductor device changes to the specific mode, e.g., a testing mode. A similar high voltage detecting circuit is disclosed in, for example, Unexamined Japanese Patent Publication (Kokai) No. 60-124124.
When a potential of a power line (hereinafter referred to as a power line potential) of the semiconductor device is stabilized, the prior high voltage detecting circuit, as in Unexamined Japanese Patent Publication No. 60-124124, generates or does not generate the control signal exactly in accordance with the potential applied from an another device to the terminal of the semiconductor device. That is, when the potential of the terminal of the semiconductor device is within the predetermined range of the normal input voltage, the prior high voltage detecting circuit does not generate the control signal for starting the specific mode of the device. When the potential of the terminal of the semiconductor device is higher by the predetermined value than the normal input voltage, the prior high voltage detecting circuit generates the control signal and the semiconductor device changes to the specific mode, e.g., the testing mode.
When, however, the power line potential of the semiconductor device is not stabilized, for example, the semiconductor device is switched ON and the power line potential of the device gradually increased, while the normal mode signal of the normal input voltage is continuously applied to the terminal of the semiconductor device, and thus the normal mode signal of the terminal of the semiconductor device may be higher by the predetermined value than the increased power line potential. That is, the normal signal of the normal input voltage is considered to be the control signal for starting the specific mode of the semiconductor device. Consequently, the prior high voltage detecting circuit may generate an error control signal without receiving the specific mode signal, and the semiconductor device may be changed to the specific mode by the error control signal.